1. Field of the Invention
The present invention is in the field of producing reaction gases and utilizing the reaction gases in metallurgical reduction processes. The specific improvement of the present invention involves recycling at least a portion of the exhaust gases from the metallurgical reduction process back into the original reactor to serve as a coolant gas for the nozzles in the reactor.
2. Description of the Prior Art
This invention relates to a method for the production of reaction gases by means of gasification of solid, liquid, or gaseous carbonaceous sources by means of a molten metal bath into which the carbonaceous sources, slag formers, and oxygen or an oxygen-containing gas used as a suspending medium are blown in through one or more jets below the surface of the molten metal and are converted into a reaction gas consisting essentially of CO and H.sub.2. These reaction gases are further supplied in a separate process stage to a metallurgical reduction wherein such reaction gases are oxidized to produce some CO.sub.2 and H.sub.2 O, while retaining some residual CO and H.sub.2.
In the use of reaction gases consisting essentially of CO and H.sub.2, particularly in the field of metallurgical reduction processes as in the direct reduction of iron ores in a reduction furnace, the reduction gases are brought into contact with the iron ore to be reduced at temperatures of approximately 1000.degree. C. During the reaction, the reduction gases are essentially utilized only up to about 40% which means that the exhaust gases leaving the reduction stack still contain significant amounts of CO and H.sub.2 as well as the CO.sub.2 and H.sub.2 O formed by the oxidation processes. These exhaust gases which still contain usable amounts of CO and H.sub.2 have either been subsequently burned to recover the sensible heat or they were utilized together with natural gas in a fission reactor to serve as a medium for the decomposition of methane gas. Another use for the exhaust gases involves washing the exhaust gases from the reduction stack to remove carbon dioxide and a further removal of the water, followed by a recycle of the remaining gases to the reduction stage for reducing iron ore. Such possibilities of utilizing the exhaust gases from the metallurgical reduction process are, however, for the most part unsatisfactory from the standpoint of energy usage and economy.
In the case of one known method, described in German AS No. 2,401,909 for the production of steel from finely granular iron ores, solid carbon carriers, lime, slag formers, oxygen, and sponge iron are introduced into a metal melt by means of multi-jacket jets arranged under the bath surface in direct proximity to one another. The reaction gases generated in the iron bath reactor are used for pre-reduction whereby the exhaust gases produced upon oxidation, particularly CO.sub.2 and H.sub.2 O are supplied to a combustion chamber for post-combustion and their residual heat is utilized by means of heat exchange. A particular disadvantage in the case of this method is that the exhaust gas is utilized only indirectly in a conventional manner with heat exchangers, and is not used directly for the production of additional reaction gases. In addition, in this particular method, there is a high oxygen consumption.
In German OS No. 2,710,106 there is described a method for the generation of liquid pig iron in a blast furnace wherein iron oxide is reduced by means of CO and H.sub.2. These reaction gases are generated separately from the blast furnace in an iron bath reactor by means of gasification of heavy oil with oxygen. The exhaust gases from the blast furnace according to this method are subjected to dust removal as well as a pressure wash to remove portions of the CO.sub.2 and H.sub.2 O. The gas cleaned in this manner is preheated and again directly supplied to the blast furnace. The pressure wash required for this process is expensive and also causes problems in the operating process. Further, it influences in a negative way the availability of the total plant.
In U.S. Pat. No. 4,238,226 there is described a method and apparatus for reducing particulate iron oxide and producing molten iron wherein coal and oxygen and injected into a molten iron bath to melt the iron, gasify the coal and produce a hot gas which is used as a reducing agent in a counterflow shaft furnace to reduce iron oxide pellets and/or natural ore in a continuous manner. The hot reduced iron product from the shaft furnace is discharged directly into the molten iron bath from which the molten iron product is discharged.